The purpose of this proposal is to investigate the role of band 3 and senescent cell antigen (SCA), an aging antigen that is a degradation product of band 3, in neurological aging and disease. Since SCA is intimately involved in cellular aging and removal, we will elucidate its role in neural aging and disease. We will begin by investigating band 3 structure and function in adult and aging brain. We will determine whether it undergoes the same age related changes as the anion transporter, "band 3," in other cells. The following anion transporter, band 3, changes are observed with cellular aging: increased degradation detected by immunoblotting with band 3 antibodies, decreased anion transport activity (increased Km; decreased Vmax), decreased number of high affinity ankyrin binding sites, and binding of physiologic IgG autoantibodies in situ (1- 27). In addition, the anion transporter, band 3, undergoes an as yet undefined change that results in binding of "980" antibodies to aged band 3. We will quantitate the amount of SCA IgG and amount of SCA on neural tissue of various ages. Kinetic studies will be performed on pieces of perfused brains obtained immediately and at various time intervals following death to determine whether there is an increase in SCA following cell death. Titers of antibodies to band 3, synthetic peptides of band 3 and SCA will be determined with ELISA in both serum and cerebral spinal fluid (CSF) to determine if antibodies are present to promote phagocytosis of neurons by glial cells. Mice will be used for the initial aging studies. However, results will be tested in parallel experiments on human tissue. We will compare the changes in neurological diseases such as Alzheimer's Disease (AD) to those occurring during normal brain aging. We continue working on and characterizing 5 antibodies we have that distinguish between normal human brain tissue and tissue from individuals with AD. The specific aims of the proposed research are: 1. Determine band 3 structural and functional changes during brain aging. 2. Quantitate brain band 3, altered band 3, and aging antigen content during aging. 3. Mechanism of band 3 alterations in aging. 4. Determine whether differences in serum and CSF antibodies to brain band 3 synthetic peptides and SCA are detected between young and old normal individuals (both mice and humans). 5. Determine whether differences in serum and CSF antibodies to brain band 3 peptides and SCA are detected between normal individuals and those with diseases such as Alzheimer's disease, multiple sclerosis, Huntington's chorea, and age-matched controls. 6. Develop monospecific and monoclonal antibodies to SCA, aged band 3, and breakdown products of band 3 for immunoblots, immunohistochemistry, immunoelectron microscopy, and affinity chromatography. 7. Identify structural and functional alterations in band 3 in neurological diseases such as AD. 8. Quantitate brain band 3, altered band 3, and aging antigen content in AD and other neurological diseases.